Multilayer heat shrinkable film comprising styrene polymer or a blend of styrene polymers

ABSTRACT

The present invention provides a multilayer heat shrinkable film incorporating an oxygen barrier material and layer comprising a styrene polymer or blend of styrene polymers, where the shrinkage of the film in at least one of MD, TD is at least 30% at 90° C. The invention is further directed to a method of manufacturing a bag from said multilayer heat shrinkable film.

FIELD OF THE INVENTION

This invention relates to multilayer heat shrinkable films.

This invention has particular application to such films for use inpackaging or foods such as meat, poultry and the like. However, it isenvisaged that films in accordance with the present invention may finduse in other packaging applications such as packaging for curableputties and sealants and for various types of respiring and nonrespiring cheese.

BACKGROUND OF THE INVENTION

Primal meat cuts are generally smaller than a side of beef, but largerthan the ultimate cut sold to the retail consumer. Primal cuts areprepared at the slaughter house and shipped to retail meat stores orrestaurants where they are butchered into smaller cuts of meat commonlyreferred to as sub-primal meat cuts. Sub-primal cuts, however, may alsobe prepared at the slaughterhouse.

Primal and sub-primal cuts are packaged to minimize air (i.e. oxygen)exposure and prevent meat spoilage and discoloration during shipping andhandling. One common way to package primal and sub-primal cuts andprotect them from the adverse effects of air is to shrink package thecuts in a film having good oxygen barrier properties. For example, amultilayer film having a barrier layer containing polyvinylidenechloride (PVDC) is a well-known packaging material. PVDC is known tohave excellent oxygen barrier properties. The other layers of themultilayer film function to protect the PVDC layer and provide therequisite low temperature and abrasion resistance properties, which thePVDC layer lacks. There are other types of biaxially oriented heatshrinkable multilayer films, which do not require oxygen barrierproperties, for example films to be used for shrink wrapping poultry.

Shrinkage properties may be produced in a film by biaxially stretchingthe film in the machine and transverse direction. The resulting filmwill heat shrink within a specified range of percentages such as fromabout 20 to about 50 percent at about 90° C. Preferably the shrinkageshould be more than 30 percent in at least one of machine and transversedirections at 90° C.

A multilayer heat shrinkable film may also be formed into packagingbags. Bags are generally made by transversely sealing a tubular stock ofmultilayer film and cutting or splitting the tube, or by superimposingflat sheets of multilayer film and sealing on three sides, or by endfolding flat sheets and sealing the two sides. A common type of sealused in manufacturing bags is a hot bar seal. The adjacent thermoplasticlayers, referred to as the inner layers, are sealed together byapplication of heat and pressure across the area to be sealed, usingcontact with opposing bars of which at least one is heated to cause theadjacent layers to fusion bond. Bags manufactured from a tube stockgenerally require one hot bar seal transverse to the tube. This seal isalso referred to as a bottom seal. Once the bottom seal is applied, thetube stock is transversely cut to form the mouth of the bag. Thestrength of seals may be measured by determining the time for a seal tofail when under certain conditions. For example, the seal is immersed inhot water at 95° C. and the hot water seal strength (“HWSS”) may bemeasured by a test such as that described as the “restrainedshrinkage-seal strength test” in Funderburk et al U.S. Pat. No.3,900,635.

Once meat or poultry is inserted into the bag, the package is evacuatedand the bag mouth must be sealed. At one time, the standard method forsealing a bag was to fasten a clip around the mouth of the bag. Today,impulse heat sealing techniques are employed to seal the bag mouth. Ingeneral, a bag mouth is impulse sealed by application of heat andpressure using opposing bars. At least one of the bars has a coveredwire or ribbon through which electric current is passed for a very brieftime period (hence the name “impulse”) to cause the adjacent film layersto fusion bond. Following the impulse of heat the bars are cooled whilecontinuing to hold the bag inner surfaces together to achieve adequateseal strength.

Irradiation of a multilayer film causes the various irradiated layers inthe film to cross-link. Under controlled conditions, cross-linking byirradiation not only provides a higher temperature impulse heat sealingrange, but also enhances the puncture resistance of the film. Undercontrolled conditions, polymeric multilayer films can be irradiated toproduce a cross-linked product having greater puncture resistancecharacteristics and other enhancements.

Three basic requirements of a commercial shrinkable multilayer film areas follows

-   1. Excellent optical properties, such as low haze and high gloss,    both before and after shrinkage. This is important for the better    aesthetic presentation of the product.-   2. Shrinkage at least as high as 30 percent in at least one    direction at temperatures about 90° C. This also contributes to    better presentation of the product to the consumer (in super    markets).-   3. Easy bag making of the product (reduced scrap during bag making).    This is more easily achievable when the film is comparatively stiff.

Prior art films typically used may have low haze and high gloss inunshrunk configuration, but much worse optical properties aftershrinking. Alternatively, they may keep their optical properties aftershrinkage, but do not shrink enough for an acceptable productpresentation.

Therefore, it is an object of the present invention to provide amultilayer heat shrinkable film, which optimizes the clarity-shrinkagebehaviour. It is a further object of the present invention to render thebag making process more efficient than with existing films.

These objects are solved by the subject-matter of the independentclaims. Preferred embodiments are set forth in the dependent claims.

SUMMARY OF THE INVENTION

This invention in one aspect resides broadly in a multilayer heatshrinkable film including a layer of styrene polymer or a blend ofstyrene polymers and an oxygen barrier polymer layer. The film shrinksat least 30% in at least one of machine and transverse directions bymeasuring unrestrained shrink of the stretched film at 90° C. for fiveseconds, or equivalent shrinkage thereof.

As used herein, the term “polymer” refers to the product of apolymerization reaction and is inclusive of homopolymers, copolymers,terpolymers etc.

As used herein, the term “homopolymer” is used with reference to apolymer resulting from the polymerization of a single monomer.

As used herein the term “copolymer” refers to polymers formed by thepolymerization reaction of at least two different monomers.

As used herein, the term “polypropylene” refers to any polymercomprising propylene polymerization units regardless of whether thepolymer is a homopolymer or a copolymer and further includes blends ofsuch homopolymers and copolymers.

As used herein the term “ethylene propylene copolymer” refers topolypropylene copolymerized with ethylene monomer.

As used herein the phrase “ethylene alpha-olefin copolymer” refers tosuch heterogeneous materials as linear low density polyethylene (LLDPE),linear medium density polyethylene (LMDPE) and very low and ultra lowdensity polyethylene (VLDPE and ULDPE), as well as homogeneous polymerssuch as TAFMER™ supplied by Mitsui Petrochemical corporation andmetallocene catalysed polymers such as Exact materials supplied byExxon. Other ethylene alpha olefin copolymers such as the long chainbranched homogeneous alpha olefin copolymers available from Dow ChemicalCompany, known as Affinity resins, are also included in the presentinvention. Homogeneous ethylene alpha olefin copolymers with a densityless than about 0.905 are generally called plastomers.

As used herein “EVOH” refers to ethylene vinyl alcohol copolymer.

As used herein “PVDC” refers to vinylidene chloride homopolyers andcopolymers.

As used herein, the term “polyamide” refers to high molecular weightpolymers having amide linkages along the molecular chain and refers morespecifically to synthetic polyamides such as nylons.

As used herein, the term “barrier” is used with reference to the abilityof films to serve as barrier to oxygen or other gases.

As used herein, the term “oriented” refers to a polymer containingmaterial which has been stretched at an elevated temperature, followedby being “set” in the stretched configuration by cooling the materialwhile substantially retaining the stretched dimensions.

As used herein, the phrase “heat shrinkable”, “heat shrink” and thelike, refer to the tendency of a film, especially an oriented film, toshrink upon the application of heat.

As used herein, the phrase “ethylene vinyl acetate” or EVA, refers to acopolymer formed from ethylene and vinyl acetate monomers, wherein theethylene derived units in the copolymer are present in major amounts,preferably between about 60 to about 98 percent, while the vinyl acetatederived units in the copolymer are present in minor amounts, preferablybetween about 2 and 40 percent.

As used herein, the phrase “ethylene methyl acrylate”, or EMA, refers toa copolymer formed from ethylene and methyl acrylate monomers, whereinthe ethylene derived units in the copolymer are present in majoramounts, preferably between about 60 to about 98 percent, while themethyl acrylate derived units in the copolymer are present in minoramounts, preferably between about 2 and 40 percent.

As used herein, the phrase “cycloolefin copolymer” refers to a copolymercomposed of ethylene units and/or of units comprising an alpha olefinwith a cyclic, bicyclic or multicyclic olefin. Preferably the COC is acopolymer of ethylene and norbornene.

The styrene content in the polymers used in the present invention ispreferably more than 50 wt. % of styrene in the styrene copolymer.Preferably, more than 60 wt. %, further preferably more than 70%, morethan 80% or even more than 90% by weight of styrene in the styrenecopolymer is used. In another preferred embodiment a styrene homopolymeris used.

As used herein the term “ionomer” is a copolymer of ethylene with anethylenically unsaturated acidic monomer, for instance acrylic ormethacrylic acid. The ionomer is preferably in its ionised form, theneutralizing cation being any suitable metal. A well known ionomermaterial is Surlyn from Dupont.

DETAILED DESCRIPTION OF THE INVENTION

According to a first and main aspect, the invention provides amultilayer heat shrinkable film comprising at least

-   a) a layer comprising an oxygen barrier material,-   b) a layer comprising a styrene polymer or a blend of styrene    polymers,    where the shrinkage of the film in at least one of MD, TD (machine    direction, transverse direction) is at least or more than 30% at 90°    C.

In one preferred embodiment of the invention, the layer of the styrenepolymer or blend of styrene polymers is the outer layer of thestructure, being exposed to the environment.

In a further embodiment, between the layer of the styrene polymer orblend of styrene polymers and the barrier layer there is a bonding layerwhich may include ethylene ester copolymers or ethylene alpha olefincopolymers.

Additionally, the multilayer heat shrinkable film of the invention maycomprise a heat sealable inner layer. The inner layer may be made of aheat sealable thermoplastic polymer or polymer blend. The heat sealableinner layer may be of any material conventionally used for its heatsealing capability. Heat sealable thermoplastic polymers are recognizedby those skilled in the art as being capable of heat sealing tothemselves at a variety of time, pressure and temperature conditions.For example, at a given pressure either a relatively high temperaturemay be applied briefly or a lower temperature may be applied for alonger period of time to obtain similarly suitable seals. It is to beappreciated that persons skilled in the art will be able to selectsealing parameters such as temperature, pressure and time of applicationthat depend upon such factors as the type of heat sealing equipmentused. The term “inner layer” generally relates to that side of themultilayer heat shrinkable film, which is not exposed to the environmentin a given product form (e.g. bag), but the good to be packaged.

This inner sealing layer may for instance be an alpha olefin copolymeror a blend of alpha olefin copolymers, e.g. a VLDPE, EVA, plastomer or ablend thereof. Alternatively, a styrene polymer or a blend of styrenepolymers may also be used as the inner heat sealing layer. In anotherembodiment, a cycloolefin copolymer or a blend of cycloolefin copolymerand alpha olefin copolymer may be the inner sealing layer.

Suitable polymers and copolymers may include alpha olefins such asmembers of the polyethylene family such as linear low-densitypolyethylene (LLDPE); very low-density polyethylene sometimes referredto as ultra low-density polyethylene (VLDPE and ULDPE respectively),plastomers or blends thereof. Still other suitable thermoplasticpolymers as the heat sealable inner layer include polypropylene,ethylene-propylene copolymer or an ionomer. It is to be understoodhowever that the thermoplastic polymers mentioned herein are notintended to be an exhaustive list, but merely exemplary.

In a preferred embodiment of the invention, the outer layer (directlyexposed to the environment) comprises a styrene copolymer in a blendwith a slip agent.

Preferred styrene polymers are polystyrene homopolymer, SBC (styrenebutadiene copolymers), SBS copolymers, SIS copolymers, SEBS copolymers,Ethylene Styrene interpolymers and blends thereof. Suitable materialsare K RESIN from Chevron Philips Chemical, FINACLEAR from Atofina andStyrolux from BASF. A preferred styrene homopolymer is STYRON from Dow.In one preferred embodiment, the styrene content of the material is morethan 50% by weight. This increases the stiffness of the material, thusmaking it more easy to convert.

One functional requirement of the barrier layer may be that togetherwith the other layers, the oxygen transmission rate through the entiremultilayer film may be below about 20 cc/l m²/24 hrs/atm, measured at 23C, 75% RH. This is to avoid spoilage of certain food products, forexample meat enclosed in the multilayer film package due to oxygenpassage from the environment through the film wall. This requirement maybe satisfied by numerous well-known barrier layer materials. Forexample, these may include certain of the polyamides (Nylon), hydrolyzedethylene vinyl acetate copolymer (EVOH) and preferably a vinylidenecopolymer. Vinylidene chloride-vinyl chloride (PVDC) is a commonly usedcopolymer but vinylidene chloride-methyl acrylate copolymer (MA-VDC) mayalso be used.

The thickness of the heat sealable inner thermoplastic first layer maybe between about 0.4 mils and about 2.0 mils. Thinner layers may notperform the described functions while thicker layers may not appreciablyimprove processability of the film and may reduce total filmperformance.

The barrier layer thickness may be between about 0.1 mils to about 0.5mils. Thinner barrier layers may not perform the intended functions andthicker layers do not appreciably improve performance.

Regardless of the structure of the film, one or more film additives maybe incorporated, such as slip agents, antiblock agents, colorants, odorinhibitors, oxygen inhibitors etc. The skilled in the art technician canbe well aware of these additives.

While the composition of the film may eliminate the need for irradiationof the multilayer film, it is to be understood that the multilayer heatshrinkable film in accordance with the invention may be irradiated tofurther enhance puncture and temperature resistance.

According to a preferred embodiment, the multilayer heat shrinkable filmof the invention comprises the following components:

-   a) an outer layer of a styrene amorphous copolymer-   b) an adjacent (bonding) layer of a blend of EMA copolymer, EVA    copolymer and metallocene LLDPE-   c) a barrier core layer comprising PVDC copolymer-   d) an adjacent (bonding) layer of EVA copolymer or EMA copolymer,    EVA copolymer and metallocene LLDPE-   e) an inner sealing layer comprising EVA, VLDPE, or a plastomer or a    blend thereof.

The heat shrinkable multilayer film in accordance with the presentinvention may be in the form of a tubular article or flat sheets. Themultilayer film may be formed into bags useful for the packaging ofmeats. The multilayer film may be especially useful for those bagsmanufactured by hot bar or impulse sealing, and after meat is insertedtherein, impulse heat sealing may be used to seal the mouth.

One end of the bag may be heat sealed by adhesion between contiguousinner layer surfaces in a direction transverse to the oppositely locatedsidewalls of the bag. The mouth end of the bag may be impulse heatsealable by fusion bonding between contiguous inner layer surfaces afterfilling the bag with food.

A bag from the multilayer film may be manufactured such that the innerlayer forms the inside portion of the bag while the outer layer formsthe outside portion of the bag. Accordingly, the inner layer of thetubular multilayer film may be the heat sealable layer, which is easilysealed by hot bar sealing. Moreover, because of the latter, the mouth ofthe bag may be more easily sealed by impulse heat sealing.

Thus, according to a second aspect, the invention is directed to amethod for manufacturing a bag from a multilayer shrinkable film asdefined above, comprising the steps of:

-   -   a) forming a bag, in which the inner layer of the multilayer        heatshrinkable film as defined herein forms the inside portion        of the bag while its outer layer forms the outside portion of        the bag,

-   b) inserting a good to be packaged into the bag, and

-   c) sealing the bag by hot bar or impulse sealing.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention pertains. All references mentionedherein are incorporated by reference in their entirety. In case ofconflict, the present specification, including definitions, willcontrol. In addition, the examples are illustrative only and notintended to be limiting.

EXAMPLES

In this series of tests, bags of the same size (400 mm long×230 mm wide)and of 60 micron thickness were fabricated from films comprising a heatsealable thermoplastic inner layer, an adjacent layer adhered on oneside to the sealable inner layer, an oxygen barrier layer, an adjacentlayer and an outer layer. The core layer in most tests was a vinylidenechloride copolymer type oxygen barrier. The film was the biaxiallyoriented heat shrinkable type, prepared by the double or trapped bubblemethod as broadly described in the aforementioned Palkhe U.S. Pat. No.3,456,044. In particular, all layers were simultaneously coextruded.

Certain physical properties of bags were measured by either of the testprocedures discussed below.

Shrinkage values were obtained by measuring unrestrained shrink of thestretched film at 90° C. for five seconds. Four test specimens were cutfrom a given sample of the oriented film to be tested. The specimenswere cut to 10 cm in the machine direction by 10 cm. in the transversedirection. Each specimen was completely immersed for 5 seconds in a 90°C. water bath. The distance between the ends of the shrunken specimenwas measured. The difference in the measured distance for the shrunkenspecimen and the original 10 cm was multiplied by ten to obtain thepercent of shrinkage for the specimen. The shrinkage for the fourspecimens was averaged for the MD shrinkage values of the given filmsample, and the shrinkage for the four specimens was averaged for the TDshrinkage value.

The tensile modulus compared below has been measured according to ASTM D882 with an Instron testing device. The optical properties were testedaccording to ASTM D1003(haze) and BS 2782(gloss).

The bag making testing was done with a use of a commercial bag makingmachine.

Example 1

A heat shrinkable multilayer film was produced having:

-   a) an outer layer of a styrene amorphous copolymer-   b) an adjacent layer of a blend of EMA copolymer, EVA copolymer and    metallocene LLDPE-   c) a barrier core layer-   d) an adjacent layer of EVA copolymer-   e) an inner sealing layer

More specifically

-   Outer layer: 98% S1+2% slip masterbatch, 12% of the total structure-   Adjacent layer 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 19% of the    total structure-   Barrier layer: PVDC copolymer, 11% of the total structure-   Adjacent layer: 100% E1, 12% of the total structure-   Inner sealing layer: 20% E1+10% E2+32% P1+30% V1+8% ADDITIVES, 46%    of the total structure.

Example 2

A heat shrinkable multilayer film was produced having:

-   a) an outer layer of a styrene amorphous copolymer-   b) an adjacent layer of a blend of EMA copolymer, EVA copolymer and    metallocene LLDPE-   c) a barrier core layer-   d) an adjacent layer of EMA copolymer, EVA copolymer and metallocene    LLDPE-   e) an inner sealing layer

More Specifically

-   Outer layer: 98% S1+2% slip masterbatch, 12% of the total structure-   Adjacent layer 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 19% of the    total structure-   Barrier layer: PVDC copolymer, 11% of the total structure-   Adjacent layer: 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 12% of    the total structure-   Inner sealing layer: 20% E1+10% E2+32% P1+30% V2+8% ADDITIVES, 46%    of the total structure

Comparative Example 3

As a comparative example, we use a commercial product of FLEXOPACK underthe name FMX containing no styrene.

Example 4

-   Outer layer: 98% S1+2% slip masterbatch, 12% of the total structure-   Adjacent layer 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 19% of the    total structure-   Barrier layer: PVDC copolymer, 11% of the total structure-   Adjacent layer: 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 12% of    the total structure-   Inner sealing layer: 20% E1+10% E2+32% P1+30% P2+8% ADDITIVES, 46%    of the total structure

Example 5

-   Outer layer: 98% S1+2% slip masterbatch, 12% of the total structure-   Adjacent layer 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 19% of the    total structure-   Barrier layer: PVDC copolymer, 11% of the total structure-   Adjacent layer:, 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 12% of    the total structure-   Inner sealing layer: 30% E1+62% P2+8% ADDITIVES, 46% of the total    structure

Example 6

-   Outer layer: 98% S1+2% slip masterbatch, 12% of the total struct6ure-   Adjacent layer 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 19% of the    total structure-   Barrier layer: PVDC copolymer, 11% of the total structure-   Adjacent layer: 15% M1+15% M2+45% E1+20% LL1+5% ADDITIVES, 12% of    the total structure-   Inner sealing layer: 30% E1+42% P2+20% C1+8% ADDITIVES, 46% of the    total structure

The films were e-beam radiated with a dose of 4 MRAD. TABLE 1 SHRINKAGECOMPARISONS SHRINK- SHRINK- SHRINK- SHRINK- AGE AGE AGE AGE SAMPLE 80 C.85 C. 90 C. 95 C. NOTES EXAMPLE 1 28/28 39/37 50/48 55/46 EXAMPLE 230/30 38/35 50/47 55/47 EXAMPLE 3 30/32 38/37 49/45 55/49 EXAMPLE 431/31 42/40 50/50 57/52 EXAMPLE 5 27/28 37/37 50/45 55/47 EXAMPLE 632/32 44/44 50/50 57/55

According to TABLE 1, there is practically no difference in thecomparison of shrinkage between the three different materials.

In the following table the optical property comparisons are explained.TABLE 2 HAZE AFTER SAMPLE HAZE GLOSS SHRINKAGE NOTES EXAMPLE 1 8.2 92 30Excellent clarity after shrink onto product EXAMPLE 2 9 92 36 Excellentclarity after shrink onto product EXAMPLE 3 10.5 81 40 Good clarityafter shrink onto product EXAMPLE 4 7.5 97 25 Excellent clarity aftershrink onto product EXAMPLE 5 8 95 27 Excellent clarity after shrinkonto product EXAMPLE 6 11.5 94 45 Excellent clarity after shrink ontoproduct

Measurement of tensile modulus has been also carried out, according toASTM D 882. TABLE 3 TENSILE NOTES MODULUS DURING BAG SAMPLE MD/TD NOTESMAKING EXAMPLE 1 210/195 stiff Very easy to convert EXAMPLE 2 239/209stiff Very easy to convert EXAMPLE 3 173/175 soft Convertible only withreduced machine speed. Blocks during bag making. EXAMPLE 4 205/190 Easyto convert EXAMPLE 5 230/225 Very easy to convert EXAMPLE 6 250/250 Veryeasy to convert

The resins used are explained in table 4. TABLE 4 Melt Melting IndexDensity point Type Description Manufacturer g/10 min g/cm³ ° C. E1 EVADupont 3135 X 0.35 0.93 95 E2 EVA 1005 VN2 0.40 0.928 102 V1 VLDPE DowAttane 1.00 0.912 122 SL 4100 P1 Plastomer Dow Affinity 1.0 0.885 74 VP8770 PB1 Polybutylene Shell 8640 2 118 LL1 LLDPE Atofina M3410 1 0.934123 S1 SB DK13 10 1.01 COPOLYMER M1 EMA Atofina LOTRYL 2-3.5 0.95 61copolymer 29MAO3 M2 EMA Atofina LOTRYL 0.5 0.94 70 copolymer 24MA005 P2Plastomer Dow Affinity 1 0.902 100 PL 1880 C1 Cycloolefin Ticona Topas1.02 copolymer 8007

1. A multilayer heat shrinkable film comprising at least a) a layercomprising an oxygen barrier material, and b) a layer comprising astyrene polymer or a blend of styrene polymers, where the film has amachine direction and a transverse direction and the shrinkage of thefilm in at least one of the machine direction or the transversedirection is at least 30% at 90° C.
 2. The multilayer heat shrinkablefilm of claim 1, wherein a layer of the multilaver film is an outerlayer and the layer comprising the styrene polymer or the blend ofstyrene polymers is the outer layer of the film.
 3. The multilayer heatshrinkable film of claim 1, wherein between the layer comprising thestyrene polymer or blend of styrene polymers and the barrier layer abonding layer exists.
 4. The multilayer heat shrinkable film of claim 3,wherein the bonding layer contains ethylene ester copolymers or ethylenealpha olefin copolymers.
 5. The multilayer heat shrinkable film of claim1, wherein the styrene polymer or the blend of styrene polymers ischosen from one or more of a styrene homopolymer or copolymer orterpolymer.
 6. The multilayer heat shrinkable film of claim 1, whereinat least one layer comprises a cycloolefin copolymer or a blend ofcycloolefin copolymer and alpha olefin copolymer.
 7. The multilayer heatshrinkable film of claim 1, wherein the film additionally contains aheat sealable inner layer.
 8. The multilayer heat shrinkable film ofclaim 7, wherein the heat sealable inner layer comprises a heat sealablethermoplastic polymer or polymer blend.
 9. The multilayer heatshrinkable film of claim 8, wherein the heat sealable inner layercomprises alpha olefins.
 10. The multilayer heat shrinkable film ofclaim 8, wherein the heat sealable inner layer comprises a styrenecopolymer or polypropylene, ethylene-propylene copolymer or an ionomer.11. The multilayer heat shrinkable film of claim 2, wherein the outerlayer comprises a styrene copolymer in a blend with a slip agent. 12.The multilayer heat shrinkable film of claim 1, wherein the styrenecopolymer is one or more of SBC (styrene butadiene copolymers), SBScopolymers, SIS copolymers, SEBS copolymers, Ethylene Styreneinterpolymers.
 13. The multilayer heat shrinkable film of claim 1,wherein the styrene content in one or more of the styrene polymer,copolymer or terpolymer is more than 50% by weight.
 14. The multilayerheat shrinkable film of claim 1, wherein the oxygen transmission ratethrough the entire multilayer film is below about 20 cc/l m²/24 hrs/atm.15. The multilayer heat shrinkable film of claim 1, wherein the oxygenbarrier layer comprises polyamides (Nylon), hydrolyzed ethylene vinylacetate copolymer (EVOH) or a vinylidene copolymer.
 16. The multilayerheat shrinkable film of claim 7, wherein the thickness of the heatsealable inner layer is between about 0.4 mils and about 2.0 mils. 17.The multilayer heat shrinkable film of claim 1, wherein the barrierlayer thickness is between about 0.1 mils to about 0.5 mils.
 18. Themultilayer heat shrinkable film of claim 1, wherein one or more of thelayers of the film additionally contain one or more film additives. 19.The multilayer heat shrinkable film of claim 1, wherein the heatshrinkable multilayer film is in the form of a tubular article, flatsheets or bag.
 20. The multilayer heat shrinkable film of claim 1,wherein the multilayer heat shrinkable film is irradiated.
 21. Themultilayer heat shrinkable film of claim 1, which comprises thefollowing components: a) an outer layer of a styrene amorphouscopolymer; b) an adjacent layer of a blend of EMA copolymer, EVAcopolymer and metallocene LLDPE; c) a barrier core layer comprising PVDCcopolymer; d) an adjacent layer of EVA copolymer or EMA copolymer, EVAcopolymer and metallocene LLDPE; and e) an inner sealing layercomprising EVA, VLDPE, or a plastomer or a blend thereof.
 22. Themultilayer heat shrinkable film of claim 9, wherein the alpha olefin isa member of the polyethylene family.
 23. The multilayer heat shrinkablefilm of claim 9, wherein the alpha olefin is selected from the groupconsisting of linear low-density polyethylene (LLDPE), very low andultra low density polyethylene (VLDPE and ULDPE respectively),plastomers and blends and copolymers thereof.
 24. The multilayer heatshrinkable film of claim 8 wherein the heat sealable inner layercomprises a cycloolefin copolymer or a blend of a cycloolefin copolymerand alpha olefin copolymer, or ethylene vinyl acetate, plastomers,copolymers or blends thereof.
 25. A method for manufacturing a bag froma multilayer shrinkable film of claim 1, comprising the steps of: a)forming a bag, in which the inner layer of the film forms the insideportion of the bag while the outer layer of the film forms the outsideportion of the bag, wherein said film is the multilayer heat shrinkablefilm of claim 1; b) inserting a good to be packaged into the bag; and c)sealing the bag by hot bar or impulse sealing.
 26. The multilayer heatshrinkable film of claim 5, wherein the styrene content in one or moreof the styrene polymer, copolymer or terpolymer is more than 50% byweight.
 27. The multilayer heat shrinkable film of claim 15, wherein thevinylidene copolymer comprises one or more of vinylidene chloride-vinylchloride (PVDC) or vinylidene chloride-methyl acrylate copolymer(MA-VDC).
 28. The multilayer heat shrinkable film of claim 18, whereinthe one or more film additives comprise one or more of slip agents,antiblocking agents, colorants, odor inhibitors or oxygen inhibitors.